Method of cooking sulphite cellulose



Patented Feb. 17,1931

y UNITED STATES PATENT OFFICE SERGEI-I. TSCHUWIKOWSKY AND GRIGORY I.LIACHOVETZKY, F MOSCOW, UNION 0F 1 SOCIALIST SOVIET REPUBLICS METHOD OFcooxmo sULPHIrE OELLULOSE .Applicationled November 8, 1929, Serial No.405,670, and-in Union of Socialist Soviet Republics August A very loWpercentage only of the sulphite cellulose factories uses the -heatof theliquor for preheating the Water or the cooking acid. A loW percentage ofthe factories obtains the thickening of the liquor during the process ofobtaining alcohol, tanning extract, resin and so on. In the firstmentioned process a portion of the heat of the liquor is utilized, butthe valuable products present are not utilized. In the second mentionedprocess a by-product is obtained during the thickening of the liquor,but the heat of the Waste liquor leaving the cookers is not perfectlyutilized during the process of evaporating. The thickening of thesulphite liquor is usually carried out under vacuum at loW temperatureswhich, as is well known, enhances the viscosity, impairs thecirculation, causes the separation of the products adapted to formcrusts and reduces the heat conductivity. These circumstances causetechnical diiiiculties and augment the costs in such a manner that veryoften the thickening of the liquor is renounced. As the liquor comingfrom the cookers contains about 25% of the heat consumed' in cooking,the reduction of the heat used for cooking the cellulose is materiallydependent on th-e method employed for utilizing the liquor running oil'.It therefore follows that from the standpoint of heat economy themethods of evaporating and of cookingthe cellulose are not to beseparated, as this is usually the case up to now, but must be combined.If the cellulose is directly cooked by steam leaving a steam engine ordelivered by a boiler, a device for pre-l paring the feed Water fortheboiler is now required'the capacity of which is a little greater thanthe steam consumption necessary ffr cooking the cellulose. On account ofa great quantity of additional Water required, the main-and utilizing'costs are increased, the properties of the feed water (particularly ifchemically purified) are impaired, the operation of the steam boilers isinfluenced and additional losses of heat are Y caused in the feed Waterof the boilers.

All these draw-backs and disadvantages are obviated by the use of themethod according to the present invention for cooking cellulose.

The invention is concerned with a method for cooking cellulose accordingto which the cooking of the cellulose is carried out by the vaporproduced during the evaporation of the sulphite liquor. The cooking andthe thickening of the liquor produced during the cooking form acontinuous process.

As both these processes are to be carried out simultaneously and mustnot be separated from each other, a common cycle of heat circulation isobtained under these conditions.

The evaporating device, thereby, utilizes the heat contained in theliquor delivered by the cookers, Whereas'the heat of the vapor producedby the thickening of the liquor is utilized by the cookers for cookingthe oellulose.

The evaporating devices must connected to the cooking vessels. Asaccording to the new process the thickening of the liquor is carried outunder high temperatures,

cause vapors of high temperatures are required for the cooking ofcellulose, the viscosity of the liquor is reduced, the circula tion isimproved and far better utilizing conbe directly ditions areobtainedcompared with the pres-y ent conditions. The amount of the liquoravailable for exploitation andthe amount of vapor produced de end on theprocess of cooking and on the liind of cellulose treated. Theheat ofthesecondary steam must, of course, be utilized perfectly to obtain aneconomic process. The calculation shows that, under the usualfluctuations of the liquor output, the main portion of the secondarysteamv is used for the cooking of the cellulose and only a small portionof the steam may be distributed among the other cellulose producingconsumers. In this manner, the number of the additional consumers, theamount ofthe available secondary steam and the general diagram ofoperation are determined in each casein connection with the liquoroutput, the amplitude and the kind ofthe plant. The same is true withregard to the condensate of 'the secondary steam and the heat of same.By the nevv method the volatile products contained in the secondarysteam may be obtained by fractional distillation without consuming anyadditional heat. The losses of condensate are in this cooking processlimited in the same manner as in an indirect cooking process, becausethe consumed steam coming from the boilers is returned to the boilerinvention is shown diagrammatically by way of example.

From the cookers 1 (or fromV devices for chemical treatment) thesulphite liquor flows directly by way of the piping 2 into one of theclosed and isolated vessels 3. This piping 2 as well as all otherpipings mentioned below are, in a known manner, provided with valves orother suitable devices necessary for carryino' out the new process. Bymeans of a suitable pump 5 the liquor is pumped through the pipings 4and4 to the preheater 6 and the evaporator 7. The latter and the preheatermay be of any suitable construction,.provided.that there is nopossibility of a mixing of the liquor with the heating steam and itscondensate. According to the conditions the evaporator 7 may be of amultiple effect andconsist of several units.

The evaporator 7 is heated by the exhaust steam'of the steam engine, bysteam taken from this engine or delivered directly by the steam boiler.The heating steam asses through the tube 8 into the evaporator In theevaporator 7 the secondary steam is produced the pressure andtemperature of which are suitable for the cooking of the cellulose. Thesecondary steam passes through the piping 9 and by way of the steam pipe10 reaches the Acookers 1 so as to heat them. Together with the abovementioned abundance of the secondary steam, the steam delivered bythesteam pipe may also be led to the other consumers, i. e. (1) by way ofthe pipe 11 to the preheater 6 for the liquor, (2) by way of the steampipe 12 to the evaporator 13 of the fresh water for the purpose ofproducing low pressure steam and (3) by way of the pipe 14 to otherdevices, for example to drying drums for finally drying the liquor forthe purpose of a higher preheating ofthe cooking acid and so on.

The condensate of the secondary steam passes from the evaporator 13 andfrom the preheater 6 by way of pipings 15 to the preheater 16 for thefresh water. The fresh preheater 13.

pure condensate of After leaving the preheater 16, the cooled condensateof the secondary steam passes, by way of the piping 19, into the workingplant. Before this steam is used, the volatile products may be separatedby subjecting this steam to a fractional distillation.

From the evaporator 13 for the fresh water the low pressure steam passesthrough the steam pipe v20 into a drying chamber, a heating` system andother devices of the plant and may be used as an additional distillatefor the boiler feeding. u

The condensate of the heatin steam which is led by the steam pipe 8 to t1e evaporator 7 is passed by the tube 21 to the storage tank 22. Thistank 22 may be provided with an automatically operating device 26 bywhich the purity of the condensate is controlled.

The pure condensate passes from the'storage tank 22, by way of thepiping 23, into the boiler house and serves as feed water for theboiler. In case of contamination the condensate leaves the storage tank22 by way of the pipe 24 and is used in the plant as hot water. Beforet-he condensate leaves the tank 22 through the pipe 24, the heat of thecondensate may be utilized as low pressure steam which is led away fromthe tank 22 by the pipe 25. This steam may be used in all cases in whichan absolute purity is not re uired.

The thickened liquor is led by t e tube 28 into the tank 27. What weclaim is: l 1. In a method of cooking sulphite cellu-v lose leading theliquor leaving the cookers into an evaporator, heating said evaporatorby fresh steam to evaporate said liquor and returning the vaporsproduced to the cookers.

2. In a method of cooking sulphite cellulose, leading'the liquor leavingthe cookers into an evaporator, heating said evaporator by fresh steamto evaporate said liquor and utilizing the vapors produced for anysuitable purpose.

, 3. In a method of cooking sulphite cellulose, leading the liquorleavin the cookers into an evaporator, heating said evaporator by freshsteam to evaporate said liquor, separating all volatile productscontained in the liquor coming from said `cookers by a fractionaldistillation and returning the vapors produced to the cookers.

4. In a method of cooking sulphite cellulose, leading the liquor leavingthe cookers into an'evaporator, heating said evaporator by fresh steamto evaporate Isaid liquor, separating all volatile products contained inthe liquor coming from` said cookers by a fractional distillation andutilizing the vapors produced for any suitable purpose.

In testimony whereof we have aHixed our signatures.

SERGEI I. TSCHUWIKOWSKY. GRIGORY I. LIACHOVETZKY.

